U.S. patent application number 13/213524 was filed with the patent office on 2012-07-26 for nonwoven having improved softness signals, and methods for manufacturing.
This patent application is currently assigned to THE PROCTER & GAMBLE COMPANY. Invention is credited to W. Andrew COSLETT, Kevin Ronald KANYA, John C. PARSONS.
Application Number | 20120189814 13/213524 |
Document ID | / |
Family ID | 44511615 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120189814 |
Kind Code |
A1 |
COSLETT; W. Andrew ; et
al. |
July 26, 2012 |
Nonwoven Having Improved Softness Signals, And Methods For
Manufacturing
Abstract
A method of manufacturing a nonwoven including the steps of:
forming a nonwoven web substantially comprised of continuous
fibers; applying a bonding pattern to said nonwoven web using a
smooth roll and a calender roll wherein said bonding pattern
comprises a pattern having unbonded areas; and subjecting the side
of said nonwoven web contacted by said smooth roll to a hydraulic
treatment at a pressure of between 25 and 75 bars and a total
energy of about 0.01-0.04 kwhr/kg., wherein said continuous fibers
are comprised of between 97% and 98.5% by weight of an olefin resin
comprising substantially of polypropylene and between 1.5% and 3%
by weight of a whitener.
Inventors: |
COSLETT; W. Andrew; (Drums,
PA) ; PARSONS; John C.; (Mountain Top, PA) ;
KANYA; Kevin Ronald; (Liberty Township, OH) |
Assignee: |
THE PROCTER & GAMBLE
COMPANY
Cincinnati
OH
FIRST QUALITY NONWOVENS, INC.
Great Neck
NY
|
Family ID: |
44511615 |
Appl. No.: |
13/213524 |
Filed: |
August 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61375564 |
Aug 20, 2010 |
|
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|
Current U.S.
Class: |
428/156 ;
156/209; 428/195.1 |
Current CPC
Class: |
A61F 13/51401 20130101;
A61F 2013/15715 20130101; A61F 2013/51078 20130101; B29C 59/005
20130101; B29L 2031/4878 20130101; Y10T 428/24479 20150115; Y10T
428/24802 20150115; A61F 13/51458 20130101; A61L 15/24 20130101;
B29K 2023/00 20130101; Y10T 156/1023 20150115; A61F 13/15585
20130101; A61F 13/511 20130101; A61F 13/15739 20130101; A61F
13/51476 20130101; A61F 2013/51038 20130101; A61L 15/18 20130101;
B29C 59/04 20130101; A61F 13/15731 20130101; B29K 2105/256
20130101; A61F 13/5148 20130101; Y10T 428/24612 20150115; A61F
13/51104 20130101; A61F 13/515 20130101; B29B 11/14 20130101; A61F
13/51496 20130101; A61F 13/15577 20130101; D04H 3/11 20130101 |
Class at
Publication: |
428/156 ;
428/195.1; 156/209 |
International
Class: |
B32B 3/00 20060101
B32B003/00; B29C 59/04 20060101 B29C059/04 |
Claims
1. A method of manufacturing a nonwoven comprising the steps of:
forming a nonwoven web substantially comprised of continuous
fibers; applying a bonding pattern to said nonwoven web using a
smooth roll and a calender roll wherein said bonding pattern
comprises a pattern having unbonded areas; and subjecting the side
of said nonwoven web contacted by said smooth roll to a hydraulic
treatment at a pressure of between 25 and 75 bars and a total
energy of about 0.01-0.04 kwhr/kg., wherein said continuous fibers
are comprised of between 97% and 98.5% by weight of an olefin resin
comprising substantially of polypropylene and between 1.5% and 3%
by weight of a whitener.
2. The method of claim 1 wherein said step of forming a nonwoven
web substantially comprised of continuous fibers further comprises:
forming one or more spunlaid layers wherein said continuous fibers
contain softeners.
3. The method of claim 1 wherein said continuous fibers are
comprised of about 1.75% by weight of whitener.
4. The method of claim 1 wherein said nonwoven web has a
substantially uniform distribution of whitener.
5. The method of claim 1 wherein said step of subjecting the side
of said nonwoven web contacted by said smooth roll to a hydraulic
treatment comprises: subjecting the side of said nonwoven web
contacted by said smooth roll to a first hydraulic treatment at a
pressure of about 50 bars; and subjecting the side of said nonwoven
web contacted by said smooth roll to a second hydraulic treatment
at a pressure of about 50 bars.
6. The method of claim 1 wherein said nonwoven web has basis weight
of between 18 and 32 gsm.
7. The method of claim 1 wherein said nonwoven web has a
substantially uniform distribution of whitener.
8. The method of claim 1 wherein said whitener is TiO.sub.2.
9. The method of claim 2 wherein the distribution by weight of
softeners in said nonwoven web is greater on the side of said
nonwoven web contacted by said calender roll than on the side of
said nonwoven web contacted by said smooth roll.
10. A nonwoven made using the methods of claim 1.
11. A hydroengorged nonwoven web, the nonwoven web being impressed
with a first pattern of bond impressions, the first pattern of bond
impressions defining a second pattern of unbonded raised regions,
wherein the raised regions have a Laminate Measured Height relative
the bond impressions of at least 280 .mu.m; and wherein the
nonwoven web: is formed of spunlaid fibers comprising polyolefin
and up to 3.0% by weight TiO.sub.2; has a basis weight of 30 gsm or
less; has an Opacity of 42 or greater; and has Bond Area of at
least 10%.
12. The nonwoven of claim 11 wherein the spunlaid fibers comprise
polypropylene.
15. The nonwoven of claim 12 wherein the spunlaid fibers comprise a
polypropylene blend containing softeners.
16. The nonwoven of claim 11 wherein substantially all of the
spunlaid fibers are monocomponent.
17. The nonwoven of claim 11 wherein the nonwoven web has a Tensile
Strength in the machine direction of at least 900 gf/cm.
18. The nonwoven of claim 11 wherein the nonwoven web has a Tensile
Strength in the cross direction of at least 300 gf/cm.
19. The nonwoven of claim 11 wherein the nonwoven web has a Total
Stiffness of no more than 9.0 gf.
20. The nonwoven of claim 11 wherein the first pattern of bond
impressions comprises at least two adjacent, parallel, straight
paths defined by the bond impressions, wherein a line exists along
each path, along which there are bonded lengths separated by
unbonded lengths, and the ratio of total bonded length to total
unbonded length (Bond Length Ratio) is at least 35% but less than
100%.
21. The nonwoven of claim 20 wherein the ratio of bonded distances
to unbonded distances is less than 75%.
22. The nonwoven of claim 20 wherein the ratio of bonded distances
to unbonded distances is less than 60%.
23. The nonwoven of claim 20 wherein the bond impressions forming
the paths are substantially uniform in shape, and substantially
uniformly distributed along the paths.
24. The nonwoven of claim 20 wherein the bond impressions have a
substantially parallelogram shape.
Description
RELATED APPLICATIONS
[0001] This application is a non-provisional based on U.S.
Provisional Patent Application Ser. No. 61/375,564, filed Aug. 20,
2010, the contents of which are incorporated herein by reference in
their entirety.
FIELD OF IN THE INVENTION
[0002] The present disclosure is related to patterned nonwoven webs
and methods of manufacturing the same.
BACKGROUND OF THE INVENTION
[0003] The business of manufacturing and marketing disposable
absorbent articles for personal care or hygiene (such as disposable
diapers, training pants, adult incontinence undergarments, feminine
hygiene products, breast pads, care mats, bibs, wound dressing
products, and the like) is relatively capital intensive and highly
competitive. To maintain or grow their market share and thereby
maintain a successful business, manufacturers of such articles must
continually strive to enhance their products in ways that serve to
differentiate them from those of their competitors, while at the
same time controlling costs so as to enable competitive pricing and
the offering to the market of an attractive value-to-price
proposition.
[0004] One way in which some manufacturers may seek to enhance such
products is through enhancements to softness. Parents and
caregivers naturally seek to provide as much comfort as they can
for their babies, and utilizing products such as disposable diapers
that they perceive as relatively soft provides reassurance that
they are doing what they can to provide comfort in that context.
With respect to other types of disposable absorbent articles that
are designed to be applied and/or worn close the skin, an
appearance of softness can reassure the wearer or caregiver that
the article will be comfortable.
[0005] Thus, manufacturers may devote efforts toward enhancing the
softness of the various materials used to make such products, such
as various web materials, including nonwoven web materials formed
from polymer fibers, and laminates thereof, forming the products.
Such laminates may include, for example, laminates of polymer films
and nonwoven web materials forming the backsheet components of the
products.
[0006] It is believed that humans' perceptions of softness of a
nonwoven web material can be affected by tactile signals, auditory
signals and visual signals.
[0007] Tactile softness signals may be affected by a variety of the
material's features and properties that have effect on its tactile
feel, including but not limited to loft, fiber thickness and
density, basis weight, microscopic pliability and flexibility of
individual fibers, macroscopic pliability and flexibility of the
nonwoven web as formed by the fibers, surface friction
characteristics, number of loose fibers or free fiber ends, and
other features.
[0008] Perceptions of softness also may be affected by auditory
signals, e.g., whether and to what extent the material makes
audible rustling, crinkling or other noises when touched or
manipulated.
[0009] It is believed that perceptions of softness of a material
also may be affected by visual signals, i.e., its visual
appearance. It is believed that, if a nonwoven material looks
relatively soft to a person, it is much more likely that the person
will perceive it as having relative tactile softness as well.
Visual impressions of softness may be affected by a variety of
features and properties, including but not limited to color,
opacity, light reflectivity, refractivity or absorption, apparent
thickness/caliper, fiber size and density, and macroscopic physical
surface features.
[0010] As a result of the complexity of the mix of the
above-described characteristics, to the extent softness is
considered an attribute of a nonwoven web material, it may elude
precise measurement or quantification. Although several methods for
measuring and evaluating material features that are believed to
affect softness signals have been developed, there are no standard,
universally accepted units or methods of measurement for softness.
It is a subjective, relative concept, difficult to characterize in
an objective way. Because softness is difficult to characterize, it
can also be difficult to affect in a predictable way, through
changes or adjustments to specifications in materials or
manufacturing processes.
[0011] Complicating efforts to define and enhance softness is the
fact that differing individuals will have differing individual
physiological and experiential frames of reference and perceptions
concerning what material features and properties will cause them to
perceive softness to a lesser or greater extent in a material, and
relative other materials.
[0012] Various efforts have been made to provide or alter features
of nonwoven web materials with the objective of enhancing consumer
perceptions of softness. These efforts have included selection
and/or manipulation of fiber chemistry, basis weight, loft, fiber
density, configuration and size, tinting and/or opacifying,
embossing or bonding in various patterns, etc.
[0013] For example, one approach to enhancing perceived softness of
a nonwoven web has involved simply increasing the basis weight of
the web, otherwise manufactured through a spunlaid/spunbond process
that includes formation of a batt of loose spun fibers and then
consolidating by calender-bonding in a pattern. All other variables
remaining constant, increasing the basis weight of such a web will
have the effect of increasing the number of fibers per unit surface
area, and correspondingly, increasing apparent thickness, fiber
density and/or loft. This approach might be deemed effective if the
only objective is increasing depth and/or loft signals affecting
perceptions of softness, i.e., simply increasing the basis weight
of a spunbond nonwoven is one way to increase its depth or loft.
However, among the costs involved in producing nonwoven web
material formed of polymer fibers is the cost of the polymer
resin(s) from which the fibers are spun. Higher basis weight
nonwovens require more resin to produce, and therefore, cost more
per unit. Thus, attempting to enhance perceived softness by
increasing nonwoven basis weight is incompatible with the
ever-present objective of controlling or reducing costs.
[0014] Another approach has involved forming a nonwoven web of
"bicomponent" polymer fibers, by spinning such fibers, laying them
to form a batt and then consolidating them by calender-bonding with
a pattern, to provide visual effects. Such bicomponent polymer
fibers are formed by spinnerets that have two side-by-side
sections, that express a first polymer on one side and a second
polymer on the other, to form a fiber having a cross section of the
first polymer on one side and the second polymer on the other
(hence the term "bicomponent"). The respective polymers may be
selected so as to have differing melting temperatures and/or
expansion-contraction rates. These differing attributes of the two
polymers cause the bicomponent fiber products to curl in the
spinning process, as they exit the spinnerets and cool. The
resulting curled fibers then may be laid down in a batt and
calender-bonded in a pattern. It is thought that the curl in the
fibers adds loft and fluff to the web, enhancing softness visual
and tactile softness signals.
[0015] In another approach relating to a backsheet laminate of a
film and a non-woven web, prior to lamination with a nonwoven web
the film is printed with a subtle pattern which, following
lamination with the nonwoven web, is visible therethrough and
simulates actual shading that would occur on the nonwoven web
surface under various lighting conditions, as if it actually bore a
pattern of three-dimensional surface features. The desired effect
is to enhance visual softness signals.
[0016] Still another approach has involved adding and blending in a
white tinting/opacifying agent (for example, titanium dioxide) to
the polymer used to form a base layer of fibers forming the
nonwoven web, forming the base layer, then forming additional
layers by laying down fibers formed of untinted polymer over the
base layer, to form a multi-layer batt. Following formation of the
multi-layer batt, it is calender-bonded in a pattern, and then
subjected to a hydroenhancing or hydroengorgement process to fluff
the fibers and increase caliper and loft. It was thought that the
presence of untinted, relatively translucent, shiny fibers laid
over and interspersed with the base layer of tinted fibers,
together with the hydroenhancing/hydroengorgement process, creates
visual effects tending to enhance the perception of loft and/or
depth. It is also believed that the hydroenhancing/hydroengorgement
process actually increases loft and/or caliper, enhancing visual
and tactile softness signals.
[0017] Still another approach has related to the manner in which
products are packaged. Typically, absorbent products such as
diapers and feminine hygiene products are packaged in stacked
groups.
[0018] During packaging, the stacks are usually compressed along a
direction approximately orthogonal to the major portions of the
surfaces formed by nonwovens, such that the caliper and loft of the
nonwovens tends to be reduced by compression when packaged. The
effect of the compression may subsist after removal of the product
from a package, adversely affecting softness signals. Thus, it was
thought that reducing the amount of compression in packaging would
help to preserve caliper and loft of the nonwovens, and thus
preserve the appearance of softness. It will be appreciated,
however, that reducing the compression in packaging necessarily has
the effect of either reducing the number of products per package,
or increasing package size--both of which increase the per-product
cost.
[0019] The approaches described above have had varying degrees of
success, but have left room for improvement in enhancing visual
and/or tactile softness signals. Additionally, many current methods
for enhancing softness signals in a nonwoven web have the
undesirable effect of decreasing desirable mechanical properties
such as tensile strength. Generally, it is believed that, for any
particular nonwoven web material, processing steps that increase
softness signals undesirably decrease strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1A is a perspective view of a disposable diaper shown
laid out horizontally in a relaxed state, wearer-facing surfaces
up;
[0021] FIG. 1B is a plan view of a disposable diaper shown laid out
horizontally in a stretched out, flattened state (stretched out
against elastic contraction induced by the presence of elastic
members), wearer-facing surfaces facing the viewer;
[0022] FIG. 2A is a cross section of the diaper depicted in FIGS.
1A and 1B, taken through line 2-2 in those figures;
[0023] FIG. 2B is a schematic cross section of a portion of a
laminate of a polymeric film and a nonwoven web, taken through a
path of bond impressions;
[0024] FIG. 3A is a schematic depiction of a pattern(s) that may be
machined, etched, engraved or otherwise formed on the working
surface of a calender-bonding roller;
[0025] FIG. 3B is a schematic depiction of a pattern(s) of bond
impressions that may be impressed on a nonwoven web;
[0026] FIG. 4A is an image of a nonwoven web sample taken using
equipment described in the Average Measured Height Method set forth
herein, illustrating an outline of an unbonded area; and
[0027] FIG. 4B is an image of a nonwoven web sample taken using
equipment described in the Average Measured Height Method set forth
herein, illustrating outlines of individual bond impressions.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0028] "Absorbent article" refers to devices that absorb and
contain body exudates, and, more specifically, refers to devices
that are placed against or in proximity to the body of the wearer
to absorb and contain the various exudates discharged from the
body. Absorbent articles may include diapers, training pants, adult
incontinence undergarments and pads, feminine hygiene products,
breast pads, care mats, bibs, wound dressing products, and the
like. As used herein, the term "exudates" includes, but is not
limited to, urine, blood, vaginal discharges, breast milk, sweat
and fecal matter.
[0029] "Absorbent core" means a structure typically disposed
between a topsheet and backsheet of an absorbent article for
absorbing and containing liquid received by the absorbent article.
The absorbent core may also include a cover layer or envelope. The
cover layer or envelope may comprise a nonwoven. In some examples,
the absorbent core may include one or more substrates, an absorbent
polymer material, and a thermoplastic adhesive material/composition
adhering and immobilizing the absorbent polymer material to a
substrate, and optionally a cover layer or envelope.
[0030] "Absorbent polymer material," "absorbent gelling material,"
"AGM," "superabsorbent," and "superabsorbent material" are used
herein interchangeably and refer to cross linked polymeric
materials that can absorb at least 5 times their weight of an
aqueous 0.9% saline solution as measured using the Centrifuge
Retention Capacity test (Edana 441.2-01).
[0031] "Absorbent particulate polymer material" is used herein to
refer to an absorbent polymer material which is in particulate form
so as to be flowable in the dry state.
[0032] "Absorbent particulate polymer material area" as used herein
refers to the area of the core wherein the first substrate and
second substrate are separated by a multiplicity of superabsorbent
particles. There may be some extraneous superabsorbent particles
outside of this area between the first substrate 64 and second
substrate.
[0033] "Airfelt" is used herein to refer to comminuted wood pulp,
which is a form of cellulosic fiber.
[0034] "Average Measured Height" is an average difference in
z-direction height between raised, unbonded areas, and bond
impressions, of a nonwoven web component of a laminate of a
polymeric film and a nonwoven web, measured and calculated
according to the Average Measured Height Method set forth
herein.
[0035] "Bicomponent" refers to fiber having a cross-section
comprising two discrete polymer components, two discrete blends of
polymer components, or one discrete polymer component and one
discrete blend of polymer components. "Bicomponent fiber" is
encompassed within the term "Multicomponent fiber." A Bicomponent
fiber may have an overall cross section divided into two or more
subsections of the differing components of any shape or
arrangement, including, for example, coaxial subsections,
core-and-sheath subsections, side-by-side subsections, radial
subsections, etc.
[0036] "Bond Area Percentage" on a nonwoven web is a ratio of area
occupied by bond impressions, to the total surface area of the web,
expressed as a percentage, and measured according to the Bond Area
Percentage method set forth herein.
[0037] "Bond Length Ratio" is a value expressed as percentage, and
is the ratio of the sum of lengths of a repeating series of bond
impressions on a nonwoven web along a theoretical line segment
through and connecting the bond impressions in the series, and
extending from a leading edge of the bond impression beginning the
series, to a leading edge of the bond impression beginning the next
adjacent repeating series, to the total length of the line segment,
and is determined according to the Bond Path/Bond Length Ratio
measurement method set forth herein. By way of non-limiting
illustration FIG. 3B in which length D.sub.0 is the length of a
line segment and lengths D.sub.1, D.sub.2 and D.sub.3 are lengths
along the line segment of three bond impressions in a hypothetical
repeating series of substantially identical bond impressions 100a
as shown in FIG. 3B, a Bond Length Ratio may be calculated as
[(D.sub.1+D.sub.2+D.sub.3)/D.sub.0].times.100%. It will be noted
that if all bond impressions 100a as exemplified in FIG. 3B are
identical in area, shape and spacing, any group of them in any
number along a line segment will constitute a repeating series.
However, bond impressions forming a path also may have differing
areas, shapes and/or spacing, and it may be necessary to identify a
repeating series of bond impressions of any other particular number
in order to determine Bond Length Ratio.
[0038] "Bonding roller," "calender roller" and "roller" are used
interchangeably.
[0039] "Cross direction"--with respect to a web material, refers to
the direction along the web material substantially perpendicular to
the direction of forward travel of the web material through the
manufacturing line in which the web material is manufactured.
[0040] "Disposable" is used in its ordinary sense to mean an
article that is disposed or discarded after a limited number of
usage events over varying lengths of time, for example, less than
about 20 events, less than about 10 events, less than about 5
events, or less than about 2 events.
[0041] "Diaper" refers to an absorbent article generally worn by
infants and incontinent persons about the lower torso so as to
encircle the waist and legs of the wearer and that is specifically
adapted to receive and contain urinary and fecal waste. As used
herein, term "diaper" also includes "pant" which is defined
below.
[0042] "Fiber" and "filament" are used interchangeably.
[0043] "Film"--means a skin-like or membrane-like layer of material
formed of one or more polymers, which does not have a form
consisting predominately of a web-like structure of consolidated
polymer fibers and/or other fibers.
[0044] "Length" or a form thereof, with respect to a diaper or
training pant, refers to a dimension measured along a direction
perpendicular to the waist edges and/or parallel to the
longitudinal axis.
[0045] "Machine direction"--with respect to a web material, refers
to the direction along the web material substantially parallel to
the direction of forward travel of the web material through the
manufacturing line in which the web material is manufactured.
[0046] "Monocomponent" refers to fiber formed of a single polymer
component or single blend of polymer components, as distinguished
from Bicomponent or Multicomponent fiber.
[0047] "Multicomponent" refers to fiber having a cross-section
comprising more than one discrete polymer component, more than one
discrete blend of polymer components, or at least one discrete
polymer component and at least one discrete blend of polymer
components. "Multicomponent fiber" includes, but is not limited to,
"Bicomponent fiber." A Multicomponent fiber may have an overall
cross section divided into subsections of the differing components
of any shape or arrangement, including, for example, coaxial
subsections, core-and-sheath subsections, side-by-side subsections,
radial subsections, etc.
[0048] A "nonwoven" is a manufactured sheet or web of directionally
or randomly oriented fibers, consolidated and bonded together by
friction, cohesion, adhesion or one or more patterns of bonds and
bond impressions created through localized compression and/or
application of heat or heating energy, or a combination thereof.
The term does not include fabrics which are woven, knitted, or
stitch-bonded with yarns or filaments. The fibers may be of natural
or man-made origin and may be staple or continuous filaments or be
formed in situ. Commercially available fibers have diameters
ranging from less than about 0.001 mm to more than about 0.2 mm and
they come in several different forms: short fibers (known as
staple, or chopped), continuous single fibers (filaments or
monofilaments), untwisted bundles of continuous filaments (tow),
and twisted bundles of continuous filaments (yarn). Nonwoven
fabrics can be formed by many processes such as meltblowing,
spunbonding, solvent spinning, electrospinning, and carding. The
basis weight of nonwoven fabrics is usually expressed in grams per
square meter (gsm).
[0049] "Opacity" is a numeric value relating to the ability of a
web material to transmit light therethrough, measured according the
Opacity Measurement Method set forth herein.
[0050] "Pant" or "training pant", as used herein, refer to
disposable garments having a waist opening and leg openings
designed for infant or adult wearers. A pant may be placed in
position on the wearer by inserting the wearer's legs into the leg
openings and sliding the pant into position about a wearer's lower
torso. A pant may be preformed by any suitable technique including,
but not limited to, joining together portions of the article using
refastenable and/or non-refastenable bonds (e.g., seam, weld,
adhesive, cohesive bond, fastener, etc.). A pant may be preformed
anywhere along the circumference of the article (e.g., side
fastened, front waist fastened). While the terms "pant" or "pants"
are used herein, pants are also commonly referred to as "closed
diapers," "prefastened diapers," "pull-on diapers," "training
pants," and "diaper-pants". Suitable pants are disclosed in U.S.
Pat. No. 5,246,433, issued to Hasse, et al. on Sep. 21, 1993; U.S.
Pat. No. 5,569,234, issued to Buell et al. on Oct. 29, 1996; U.S.
Pat. No. 6,120,487, issued to Ashton on Sep. 19, 2000; U.S. Pat.
No. 6,120,489, issued to Johnson et al. on Sep. 19, 2000; U.S. Pat.
No. 4,940,464, issued to Van Gompel et al. on Jul. 10, 1990; U.S.
Pat. No. 5,092,861, issued to Nomura et al. on Mar. 3, 1992; U.S.
Patent Publication No. 2003/0233082 A1, entitled "Highly Flexible
And Low Deformation Fastening Device", filed on Jun. 13, 2002; U.S.
Pat. No. 5,897,545, issued to Kline et al. on Apr. 27, 1999; U.S.
Pat. No. 5,957,908, issued to Kline et al on Sep. 28, 1999.
[0051] "Substantially cellulose free" is used herein to describe an
article, such as an absorbent core, that contains less than 10% by
weight cellulosic fibers, less than 5% cellulosic fibers, less than
1% cellulosic fibers, no cellulosic fibers, or no more than an
immaterial amount of cellulosic fibers. An immaterial amount of
cellulosic material would not materially affect the thinness,
flexibility, or absorbency of an absorbent core.
[0052] "Substantially continuously distributed" as used herein
indicates that within the absorbent particulate polymer material
area, the first substrate 64 and second substrate 72 are separated
by a multiplicity of superabsorbent particles. It is recognized
that there may be minor incidental contact areas between the first
substrate 64 and second substrate 72 within the absorbent
particulate polymer material area. Incidental contact areas between
the first substrate 64 and second substrate 72 may be intentional
or unintentional (e.g. manufacturing artifacts) but do not form
geometries such as pillows, pockets, tubes, quilted patterns and
the like.
[0053] "Tensile Strength" refers to the maximum tensile force (Peak
Force) a material will sustain before tensile failure, as measured
by the Tensile Strength Measurement Method set forth herein.
[0054] "Thickness" and "caliper" are used herein
interchangeably.
[0055] "Total Stiffness" refers to the measured and calculated
value relating to a material, according to the Stiffness
measurement method set forth herein.
[0056] "Width" or a form thereof, with respect to a diaper or
training pant, refers to a dimension measured along a direction
parallel to the waist edges and/or perpendicular to the
longitudinal axis.
[0057] "Z-direction," with respect to a web, means generally
orthogonal or perpendicular to the plane approximated by the web in
the machine and cross direction dimensions.
[0058] Examples of the present invention include disposable
absorbent articles having improved softness attributes.
[0059] FIG. 1A is a perspective view of a diaper 10 in a relaxed,
laid-open position as it might appear opened and lying on a
horizontal surface. FIG. 1B is a plan view of a diaper 10 shown in
a flat-out, uncontracted state (i.e., without elastic induced
contraction), shown with portions of the diaper 10 cut away to show
underlying structure. The diaper 10 is depicted in FIG. 1B with its
longitudinal axis 36 and its lateral axis 38. Portions of the
diaper 10 that contact a wearer are shown oriented upwards in FIG.
1A, and are shown facing the viewer in FIG. 1B. FIG. 2A is a cross
section of the diaper taken at line 2-2 in FIG. 1B.
[0060] The diaper 10 generally may comprise a chassis 12 and an
absorbent core 14 disposed in the chassis. The chassis 12 may
comprise the main body of the diaper 10.
[0061] The chassis 12 may include a topsheet 18, which may be
liquid pervious, and a backsheet 20, which may be liquid
impervious. The absorbent core 14 may be encased between the
topsheet 18 and the backsheet 20. The chassis 12 may also include
side panels 22, elasticized leg cuffs 24, and an elastic waist
feature 26. The chassis 12 may also comprise a fastening system,
which may include at least one fastening member 46 and at least one
landing zone 48.
[0062] The leg cuffs 24 and the elastic waist feature 26 may each
typically comprise elastic members 28. One end portion of the
diaper 10 may be configured as a first waist region 30 of the
diaper 10. An opposite end portion of the diaper 10 may be
configured as a second waist region 32 of the diaper 10. An
intermediate portion of the diaper 10 may be configured as a crotch
region 34, which extends longitudinally between the first and
second waist regions 30 and 32. The crotch region 34 may include
from 33.3% to 50% of the overall length of the diaper 10, and each
of waist regions 30, 32 may correspondingly include from 25% to
33.3% of the overall length of the diaper 10.
[0063] The waist regions 30 and 32 may include elastic elements
such that they gather about the waist of the wearer to provide
improved fit and containment (elastic waist feature 26). The crotch
region 34 is that portion of the diaper 10 which, when the diaper
10 is worn, is generally positioned between the wearer's legs.
[0064] The diaper 10 may also include such other features including
front and rear ear panels, waist cap features, elastics and the
like to provide better fit, containment and aesthetic
characteristics. Such additional features are described in, e.g.,
U.S. Pats. Nos. 3,860,003 and 5,151,092.
[0065] In order to apply and keep diaper 10 in place about a
wearer, the second waist region 32 may be attached by the fastening
member 46 to the first waist region 30 to form leg opening(s) and
an article waist. When fastened, the fastening system carries a
tensile load around the article waist.
[0066] According to some examples, the diaper 10 may be provided
with a re-closable fastening system or may alternatively be
provided in the form of a pant-type diaper. When the absorbent
article is a diaper, it may comprise a re-closable fastening system
joined to the chassis for securing the diaper to a wearer. When the
absorbent article is a pant-type diaper, the article may comprise
at least two side panels joined to the chassis and to each other to
form a pant. The fastening system and any component thereof may
include any material suitable for such a use, including but not
limited to plastics, films, foams, nonwoven, woven, paper,
laminates, stretch laminates, activated stretch laminates, fiber
reinforced plastics and the like, or combinations thereof. In some
examples, the materials making up the fastening device may be
flexible. In some examples, the fastening device may comprise
cotton or cotton-like materials for additional softness or consumer
perception of softness. The flexibility may allow the fastening
system to conform to the shape of the body and thus, reduce the
likelihood that the fastening system will irritate or injure the
wearer's skin.
[0067] For unitary absorbent articles, the chassis 12 and absorbent
core 14 may form the main structure of the diaper 10 with other
features added to form the composite diaper structure. While the
topsheet 18, the backsheet 20, and the absorbent core 14 may be
assembled in a variety of well-known configurations, preferred
diaper configurations are described generally in U.S. Pat. No.
5,554,145 entitled "Absorbent Article With Multiple Zone Structural
Elastic-Like Film Web Extensible Waist Feature" issued to Roe et
al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled "Disposable
Pull-On Pant" issued to Buell et al. on Oct. 29, 1996; and U.S.
Pat. No. 6,004,306 entitled "Absorbent Article With
Multi-Directional Extensible Side Panels" issued to Robles et al.
on Dec. 21, 1999.
[0068] The topsheet 18 may be fully or partially elasticized and/or
may be foreshortened to create a void space between the topsheet 18
and the absorbent core 14. Exemplary structures including
elasticized or foreshortened topsheets are described in more detail
in U.S. Pat. No. 5,037,416 entitled "Disposable Absorbent Article
Having Elastically Extensible Topsheet" issued to Allen et al. on
Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled "Trisection
Topsheets for Disposable Absorbent Articles and Disposable
Absorbent Articles Having Such Trisection Topsheets" issued to
Freeland et al. on Dec. 14, 1993.
[0069] The backsheet 20 may be joined with the topsheet 18. The
backsheet 20 may serve prevent the exudates absorbed by the
absorbent core 14 and contained within the diaper 10 from soiling
other external articles that may contact the diaper 10, such as bed
sheets and clothing. Referring to FIG. 2B, the backsheet 20 may be
substantially impervious to liquids (e.g., urine) and comprise a
laminate of a nonwoven 21 and a thin polymeric film 23 such as a
thermoplastic film having a thickness of about 0.012 mm (0.5 mil)
to about 0.051 mm (2.0 mils). Suitable backsheet films include
those manufactured by Tredegar Industries Inc. of Terre Haute, Ind.
and sold under the trade names X15306, X10962, and X10964. Other
suitable backsheet materials may include breathable materials that
permit vapors to escape from the diaper 10 while still preventing
liquid exudates from passing through the backsheet 20. Exemplary
breathable materials may include materials such as woven webs,
nonwoven webs, composite materials such as film-coated nonwoven
webs, and microporous films such as manufactured by Mitsui Toatsu
Co., of Japan under the designation ESPOIR and by EXXON Chemical
Co., of Bay City, Tex., under the designation EXXAIRE. Suitable
breathable composite materials comprising polymer blends are
available from Clopay Corporation, Cincinnati, Ohio under the name
HYTREL blend Pl 8-3097. Other examples of such breathable composite
materials are described in greater detail in PCT Application No. WO
95/16746, published on Jun. 22, 1995 in the name of E. I. DuPont.
Other breathable backsheets including nonwoven webs and apertured
formed films are described in U.S. Pat. No. 5,571,096 issued to
Dobrin et al. on Nov. 5, 1996.
[0070] In some examples, the backsheet of the present invention may
have a water vapor transmission rate (WVTR) of greater than about
2,000 g/24 h/m2, greater than about 3,000 g/24 h/m2, greater than
about 5,000 g/24 h/m2, greater than about 6,000 g/24 h/m2, greater
than about 7,000 g/24 h/m2, greater than about 8,000 g/24 h/m2,
greater than about 9,000 g/24 h/m2, greater than about 10,000 g/24
h/m2, greater than about 11,000 g/24 h/m2, greater than about
12,000 g/24 h/m2, greater than about 15,000 g/24 h/m2, measured
according to WSP 70.5 (08) at 37.8.degree. C. and 60% Relative
Humidity.
[0071] Suitable non-woven materials useful in the present invention
include, but are not limited to SMS material, comprising a
spunbonded, a melt-blown and a further spunbonded layer. In some
examples, permanently hydrophilic non-wovens, and in particular,
nonwovens with durably hydrophilic coatings may be desirable.
Another suitable embodiment comprises a SMMS-structure. In some
examples, the non-wovens may be porous.
[0072] In some examples, suitable non-woven materials may include,
but are not limited to synthetic fibers, such as PE, PET, and PP.
As polymers used for nonwoven production may be inherently
hydrophobic, they may be coated with hydrophilic coatings. One way
to produce nonwovens with durably hydrophilic coatings, is via
applying a hydrophilic monomer and a radical polymerization
initiator onto the nonwoven, and conducting a polymerization
activated via UV light resulting in monomer chemically bound to the
surface of the nonwoven as described in co-pending U.S. Patent
Publication No. 2005/0159720. Another way to produce nonwovens with
durably hydrophilic coatings is to coat the nonwoven with
hydrophilic nanoparticles as described in co-pending applications
U.S. Pat. No. 7,112,621 to Rohrbaugh et al. and in PCT Application
Publication WO 02/064877.
[0073] Typically, nanoparticles have a largest dimension of below
750 nm. Nanoparticles with sizes ranging from 2 to 750 nm may be
economically produced. An advantage of nanoparticles is that many
of them can be easily dispersed in water solution to enable coating
application onto the nonwoven, they typically form transparent
coatings, and the coatings applied from water solutions are
typically sufficiently durable to exposure to water. Nanoparticles
can be organic or inorganic, synthetic or natural. Inorganic
nanoparticles generally exist as oxides, silicates, and/or
carbonates. Typical examples of suitable nanoparticles are layered
clay minerals (e.g., LAPONITE.TM. from Southern Clay Products, Inc.
(USA), and Boehmite alumina (e.g., Disperal P2.TM. from North
American Sasol. Inc.). According to one example, a suitable
nanoparticle coated non-woven is that disclosed in the co-pending
patent application Ser. No. 10/758,066 entitled "Disposable
absorbent article comprising a durable hydrophilic core wrap" by
Ponomarenko and Schmidt.
[0074] Further useful non-wovens are described in U.S. Pat. No.
6,645,569 to Cramer et al., U.S. Pat. No. 6,863,933 to Cramer et
al., U.S. Pat. No. 7,112,621 to Rohrbaugh et al., and co-pending
patent application Ser. Nos. 10/338,603 to Cramer et al. and
10/338,610 to Cramer et al. In some cases, the nonwoven surface can
be pre-treated with high energy treatment (corona, plasma) prior to
application of nanoparticle coatings. High energy pre-treatment
typically temporarily increases the surface energy of a low surface
energy surface (such as PP) and thus enables better wetting of a
nonwoven by the nanoparticle dispersion in water.
[0075] Notably, permanently hydrophilic non-wovens are also useful
in other parts of an absorbent article. For example, topsheets and
absorbent core layers comprising permanently hydrophilic non-wovens
as described above have been found to work well.
[0076] According to one example, the nonwoven may comprise a
material that provides good recovery when external pressure is
applied and removed. Further, according to one example, the
nonwoven may comprise a blend of different fibers selected, for
example from the types of polymeric fibers described above. In some
embodiments, at least a portion of the fibers may exhibit a spiral
curl which has a helical shape. In some examples, the nonwoven may
comprise fibers having different degrees or types of curling, or
both. For example, one embodiment may include a mixture of fibers
having about 3 to about 5 curls per centimeter (cpc) or about 3.5
to about 4 cpc, and other fibers having about 1.5 to about 3.2 cpc
or about 2 to about 2.8 cpc.
[0077] Different types of curls include, but are not limited to a
2D curl or "flat curl" and a 3D or spiral-curl. According to one
example, the fibers may include bicomponent fibers, which are
individual fibers each comprising different materials, usually a
first and a second polymeric material.
[0078] It is believed that the use of side-by-side bi-component
fibers is beneficial for imparting a spiral curl to the fibers.
[0079] In order to enhance softness perceptions of the absorbent
article, nonwovens forming the backsheet may be hydroenhanced or
hydroengorged. Hydroenhanced/hydroengorged nonwovens are described
in U.S. Pats. Nos. 6,632,385 and 6,803,103, and U.S. Pat. App. Pub.
No. 2006/0057921.
[0080] A nonwoven may also be treated by a "selfing" mechanism. By
"selfing" nonwovens, high densities of loops (>150 in 2) may be
formed which protrude from the surface of the nonwoven substrate.
Since these loops act as small flexible brushes, they create an
additional layer of springy loft, which may enhance softness.
Nonwovens treated by a selfing mechanism are described in U.S. Pat.
App. Pub. No. US 2004/0131820.
[0081] Nonwovens also may include a surface coating. In one
example, the surface coating may include a fiber surface modifying
agent, that reduces surface friction and enhances tactile
lubricity. Preferred fiber surface modifying agents are described
in U.S. Pat. Nos. 6,632,385 and 6,803,103; and U.S. Pat. App. Pub.
No. 2006/0057921.
[0082] A surface coating also may include a surfactant coating. One
such surfactant coating is available from Schill & Silacher
GmbH, Boblingen, Germany, under the Tradename Silastol PST.
[0083] Any of the nonwovens described herein may be used for the
topsheet, backsheet, or any other portion of the absorbent article
comprising a nonwoven. In order to achieve improved softness of the
absorbent article, the nonwovens of the present invention may have
a basis weight of greater than about 20 gsm, greater than about 22
gsm, greater than about 24 gsm, greater than about 26 gsm, greater
than about 28 gsm, greater than about 30 gsm, greater than about 32
gsm.
[0084] The absorbent core generally may be disposed between the
topsheet 18 and the backsheet 20. It may include one or more
layers, such as a first absorbent layer 60 and a second absorbent
layer 62.
[0085] The absorbent layers 60, 62 may include respective
substrates 64, 72, an absorbent particulate polymer material 66, 74
disposed on substrates 64, 72, and a thermoplastic adhesive
material 68, 76 disposed on and/or within the absorbent particulate
polymer material 66, 74 and at least portions of the substrates 64,
72 as an adhesive for immobilizing the absorbent particulate
polymer material 66, 74 on the substrates 64, 65.
[0086] The substrate 64 of the first absorbent layer 60 may be
referred to as a dusting layer and has a first surface which faces
the backsheet 20 and a second surface which faces the absorbent
particulate polymer material 66. Likewise, the substrate 72 of the
second absorbent layer 62 may be referred to as a core cover and
has a first surface facing the topsheet 18 and a second surface
facing the absorbent particulate polymer material 74.
[0087] The first and second substrates 64 and 72 may be adhered to
one another with adhesive about the periphery to form an envelope
about the absorbent particulate polymer materials 66 and 74 to hold
the absorbent particulate polymer material 66 and 74 within the
absorbent core 14.
[0088] The substrates 64, 72 may be of one or more nonwoven
materials, and may be liquid permeable.
[0089] As illustrated in FIG. 2A, the absorbent particulate polymer
material 66, 74 may be deposited on the respective substrates 64,
72 in clusters 90 of particles to form a grid pattern comprising
land areas 94 and junction areas 96 between the land areas 94. Land
areas 94 are areas where the thermoplastic adhesive material does
not contact the nonwoven substrate or the auxiliary adhesive
directly; junction areas 96 are areas where the thermoplastic
adhesive material does contact the nonwoven substrate or the
auxiliary adhesive directly. The junction areas 96 in the grid
pattern contain little or no absorbent particulate polymer material
66 and 74. The land areas 94 and junction areas 96 can have a
variety of shapes including, but not limited to, circular, oval,
square, rectangular, triangular, and the like. First and second
layers 60, 62 may be combined to form the absorbent core 14.
Preferred absorbent articles and cores are described in U.S.
application Ser. No. 12/141,122; U.S. Pat. Apps. Pub. Nos.
2004/0167486A1 and 2004/0162536; and PCT Pub. No. WO
2009/060384.
[0090] Signal ingredients may be incorporated into one or more
components of the absorbent article. Signal ingredients may
include, but are not limited to, vitamins A, E, D, and C,
panthenol, niacin, omega 3 oils, cocoa butter, beeswax, cashmere,
sweet almond oil, jojoba, oatmeal, aloe, cotton, honey, and silk.
These signal ingredients may be added to an absorbent article for
the purpose of signaling a benefit to the consumer. As an example,
one or more of these signal ingredients may be added to a lotion
that may be applied to an absorbent article component. The signal
ingredient alone, or in a lotion, may be applied to the topsheet,
backsheet, or any other component of the absorbent article. The
lotion may comprise less than about 0.1% by weight, less than about
0.01% by weight, less than about 0.006% by weight, less than about
0.005% by weight, less than about 0.004% by weight, less than about
0.003% by weight, less than about 0.002% by weight, and less than
about 0.001% by weight of the signal ingredient.
[0091] Additionally, a signal ingredient may, in combination with
other absorbent article features, result in an unexpected synergy
for communicating a benefit to the consumer. As an example,
consumers may respond unexpectedly more favorably to an absorbent
article that is thin and perceptibly soft in combination with a
communication that lotion in the diaper comprises vitamin E than
they would respond to either communication on its own.
[0092] An example of a diaper lotion comprising vitamin E as a
signal ingredient may include the following formula: PET/StOH Mix
(ratio=1.41) 94.0% to 99.8% (by weight) Aloe Extract 0.1% to 3.0%
(by weight) Vitamin E 0.001% to 0.1% (by weight). Further, vitamin
E may be used in its natural form or esters of natural vitamin E
may be used (e.g., vitamin E acetate). U.S. App. Pub. Nos.
2002/0143304; 2004/0175343; 2003/0077307; U.S. Pat. Nos. 5,643,588;
5,635,191; 5,607,760; 6,861,571; and PCT Application Nos. WO
00/69481; and WO 98/24391 disclose various absorbent article
lotions that signal ingredients may be added to.
[0093] Another way to achieve improved softness of the absorbent
article may be through a lower in-bag compression. Lower
compression rates result in a softer feeling absorbent article.
Preferred in-bag compression percentages of the present invention
are less than about 54%, less than about 52%, less than about 50%,
less than about 49%, less than about 48%, less than about 47%, less
than about 46%. For purposes herein, in-bag compression percentage
is determined according to the In-Bag Compression Measurement Test
set forth below.
[0094] Enhanced Nonwoven Webs Used for Topsheets and/or Backsheet
Laminates
[0095] The foregoing description describes features of an absorbent
article, any combination of which can be employed to enhance
consumer perceptions of softness of the article. In addition,
however, it is believed that manufacturing a nonwoven web, which
may be used as a component of an absorbent article including, e.g.,
a topsheet 18 and/or backsheet 20 (see FIGS. 2A, 2B), according to
the following description, provides for enhancement of softness
signals of the component, and has synergistic effects with respect
to enhancing perceptions of softness of the article as a whole. At
the same time, counterintuitively, features described below enhance
tensile strength of the nonwoven web, and consequently, of the
topsheet, backsheet or other component formed of it. When
attempting to improve softness signals, preserving or enhancing
tensile strength of a nonwoven may be of particular interest in
absorbent articles for at least two reasons. First, the nonwoven
web may typically be required to sustain certain minimum tensile
forces and undergo sufficiently low changes in dimension so as to
be effectively processable in downstream manufacturing operations.
Second, the nonwoven web typically may be a substantial contributor
to structural integrity of a backsheet laminate in absorbent
products such as disposable diapers, in which the backsheet may be
required to sustain forces resulting from application/donning on a
wearer (e.g., when a caregiver tugs on fastening members to apply a
diaper), wearer movements, and bulk and weight and bulk contained
and sustained by the backsheet when the diaper is loaded with the
wearer's exudates.
[0096] As previously noted, a backsheet 20 may be formed of a
laminate of a nonwoven and a thin polymeric film. In some examples,
the polymeric film may have a thickness of about 0.012 mm (0.5 mil)
to about 0.051 mm (2.0 mils). In order to achieve the desired
overall visual appearance, the opacity and whiteness of the
backsheet laminate may be enhanced by addition of, for example,
calcium carbonate (CaCO.sub.3) to the film during its formation.
Inclusion of fine particles of CaCO.sub.3 cause the formation of
micropores about the particles upon stretching, or biaxial
stretching in processing of the film, which serve to make the
resulting film air- and vapor-permeable (thus, "breathable",
reducing the likelihood of skin overhydration and thereby reducing
the likelihood of conditions such as diaper rash). The CaCO.sub.3
particles and the resulting micropores in the film also serve to
enhance its opacity. Examples of suitable films include MICROPRO
microporous films, and films designated BR137P and BR137U,
available from Clopay Corporation, Mason, Ohio.
[0097] In some examples, the polymeric film may be formed of
components, and as described, in U.S. application Pub. No.
2008/0306463, and may include some or all of the features and/or
components described therein, that reduce the film's vulnerability
to glue "burn-through."
[0098] The nonwoven web may be a hydroengorged spunbond nonwoven
with a quilted bonding pattern and possessing two-sided properties
due to a combination of materials and hydraulic treatment. The
nonwoven may be formed to have an outer-facing side/surface having
a pronounced quilted appearance and enhanced softness attributes,
whereas the inner-facing side/surface many not necessarily require
enhanced softness attributes.
[0099] The nonwoven web may be formed from one or more resins of
polyolefins including but not limited to polypropylene (PP),
polyethylene (PE), and polyethylene terephthalate (PET), and blends
thereof. Resins including polypropylene may be particularly useful
because of polypropylene's relatively low cost and surface friction
properties of fibers formed from it (i.e., they have a relatively
smooth, slippery tactile feel). Resins including polyethylene may
also be desirable because of polyethylene's relative
softness/pliability and even more smooth/slippery surface friction
properties. Relative each other, PP currently has a lower cost and
fibers formed from it have a greater tensile strength, while PE
currently has a greater cost and fibers formed from it have a lower
tensile strength but greater pliability and a more smooth/slippery
feel. Accordingly, it may be desirable to form nonwoven web fibers
from a blend of PP and PE resins, finding a balance of the best
proportions of the polymers to balance their advantages and
disadvantages. In some examples, the fibers may be formed of PP/PE
blends such as described in U.S. Pat. No. 5,266,392. A suitable
spunbond nonwoven may be formed in multiple layers containing
differing materials. For example, the spunbond nonwoven may have a
standard polypropylene forming the layers on the inner-facing side
of the nonwoven, and a polypropylene blend containing softeners for
the layers of the outer-facing side of the nonwoven. An exemplary
polypropylene blend containing softeners is ExxonMobil SFT-315;
however other resins and resin blends designed for use in
manufacturing soft nonwovens may also be used.
[0100] A nonwoven may be formed from any of these resins by
conventional spunbonding processes, in which the resin(s) are
heated and forced under pressure through spinnerets. The spinnerets
eject fibers of the polymer(s), which are then directed onto a
moving belt; as they strike the moving belt they are laid down in
somewhat random orientations to form a spunlaid batt. The batt then
may be calender-bonded to form the nonwoven web.
[0101] Nonwovens formed of any basis weight may be used. However,
as noted in the background, relatively higher basis weight, while
having relatively greater apparent caliper and loft, also has
relatively greater cost. On the other hand, relatively lower basis
weight, while having relatively lower cost, adds to the difficulty
of providing a backsheet that has and sustains a dramatic visual
quilted appearance following compression in a package. It is
believed that the combination of features described herein strikes
a good balance between controlling material costs and providing a
dramatic visual quilted appearance when the basis weight of the
nonwoven used is 30 gsm or less, preferably from 20 to 30 gsm, or
even more preferably from 23 to 27 gsm.
[0102] It is believed that the desired overall visual softness
signals of a backsheet laminate may be better achieved when the
backsheet laminate is substantially white in color, and has an
Opacity of at least 65, more preferably at least 70, even more
preferably at least 73, and still more preferably at least 75, as
measured by the Opacity Measurement Method set forth below.
Accordingly, it may be desirable to add a white-tinting/opacifying
agent also to the polymer(s) forming the polymeric film, and to all
of the polymer(s) supplying all of the spinnerets.
[0103] With respect to a nonwoven web that may form a component of
an absorbent article including a topsheet or a backsheet, it was
previously believed that adding a white tinting agent to only the
polymer(s) forming a first, underlying layer of spunlaid fibers,
while adding none to the polymer(s) forming one or more of the
overlying spunlaid layers, helped enhance visual softness
attributes as a result of the relatively translucent, shiny
untinted fibers interacting with ambient light and the white-tinted
underlying fibers. However, it has been surprisingly discovered
that the desired visual quilted appearance, manifest in a more
dramatic visual "popping out" of the impressed pattern, may be more
effectively enhanced when substantially all fibers forming the
nonwoven are white-tinted/opacified, rather than just one layer, or
only some of them. Accordingly, it is believed desirable that a
white-tinting/opacifying agent be added to all polymer resin that
is spun to make the nonwoven, rather than just that portion of
resin that is supplied to a first beam or die leading to a first
bank of spinnerets. It is believed that adjusting the opacity of
the nonwoven web, through addition of an opacifying agent, may be
desirable, such that the nonwoven web has an Opacity of at least
36, more preferably at least 42, and still more preferably at least
45.
[0104] While a variety of whitening/opacifying agents may suffice,
it is believed that titanium dioxide (TiO.sub.2) may be
particularly effective because of its brightness and relatively
high refractive index. It is believed that addition of TiO.sub.2 to
the polymer(s) from which the fibers are to be formed, in an amount
up to 5.0% by weight of the nonwoven, may be effective to achieve
the desired results. However, because TiO.sub.2 is a relatively
hard, abrasive material, inclusion of TiO.sub.2 in amounts greater
than 5.0% by weight may have deleterious effects, including wear
and/or clogging of spinnerets; interruption and weakening of the
structure of the fibers and/or calender bonds therebetween;
undesirably increasing the surface friction properties of the
fibers (resulting in a less smooth tactile feel); and unacceptably
rapid wear of downstream processing equipment components. While
5.0% by weight TiO.sub.2 may be an upper limit, if may be more
desirable to include no more than 4.0% or even no more than 3.0% by
weight TiO.sub.2. In order to desirably affect the appearance of
the visible outer-facing side of the nonwoven, each layer may
include a minimum of 1.5%, to 3%, by weight TiO.sub.2, more
preferably 1.5% to 2%, and even more preferably, about 1.75%. It is
believed that the increased opacity provided by whitener added to
the layers of the outer-facing visible side helps to produce the
visually distinctive appearance of the nonwoven.
[0105] Spunbonding includes the step of calender-bonding the batt
of spunlaid fibers, to consolidate them and bond them together to
some extent to create a fabric-like structure and enhance
mechanical properties e.g., tensile strength, which may be
desirable so the material can sufficiently maintain structural
integrity and dimensional stability in subsequent manufacturing
processes, and in the final product in use. Calender-bonding may be
accomplished by passing the batt through the nip between a pair of
rotating calender rollers, thereby compressing and consolidating
the fibers to form a web. One or both of the rollers may be heated,
so as to promote plastic deformation, intermeshing and/or thermal
bonding/fusion between superimposed fibers compressed at the nip.
The rollers may form operable components of a bonding mechanism in
which they are urged together by a controllable amount of force, so
as to exert the desired compressing force/pressure at the nip. In
some processes heating may be deemed unnecessary, since compression
alone may generate sufficient energy within the fibers to effect
bonding, resulting from rapid deformation and frictional heat
generated in the fibers as they are urged against each other where
they are superimposed, resulting in plastic deformation and
intermeshing, and possibly thermal bonding/fusion. In some
processes an ultrasonic energy source may be included in the
bonding mechanism so as to transmit ultrasonic vibration to the
fibers, again, to generate heat energy within them and enhance
bonding.
[0106] One or both of the bonding rollers may have their
circumferential surfaces machined, etched, engraved or otherwise
formed to have thereon a pattern of protrusions and recessed areas,
so that bonding pressure exerted on the batt at the nip is
concentrated at the outward surfaces of the protrusions, and
reduced or substantially eliminated at the recessed areas. As a
result, an impressed pattern of bonds between fibers forming the
web, somewhat corresponding to the pattern of protrusions on the
roller, is formed on the nonwoven web. One roller may have a
smooth, unpatterned cylindrical surface, and the other may be
formed with a pattern as described; this combination will impart a
pattern on the web somewhat reflecting the pattern on the formed
roller. In some examples both rollers may be formed with patterns,
and in particular examples, differing patterns that work in
combination to impress a combination pattern on the web such as
described in, for example, U.S. Pat. No. 5,370,764.
[0107] A repeating pattern of protrusions and recessed areas such
as, for example, depicted in FIG. 3A, may be formed onto one
roller. The smaller shapes depicted in FIG. 3A represent outlines
of rhombus- or diamond-shaped raised surfaces 100 of protrusions,
while the areas between them represent recessed areas 101. Each
protrusion surface may be imparted with a width Wp.sub.1 (relative
the machine direction MD) and a length 4.sub.1, such that each
protrusion surface 100 has an area. Without intending to be bound
by theory, it is believed that the visual impact of the bond
impressions impressed on the web, as well as the tensile strength,
resulting from the protrusion surfaces 100, may be affected by the
area of the protrusion surfaces 100. Accordingly, it is believed
desirable that the average area of the individual protrusion
surfaces 100 be from 0.74 mm.sup.2 to 1.12 mm.sup.2, or from 0.84
mm.sup.2 to 1.02 mm.sup.2, or even from 0.88 mm.sup.2 to 0.98
mm.sup.2. Protrusion surfaces 100 may have diamond shapes as shown,
or may have any other suitable shape, although it is believed that
a diamond, rectangle, square or oval shape may have the desirable
effect of simulating the appearance of stitching, as in a
quilt.
[0108] As can be seen in FIG. 3A, protrusion surfaces 100 may be
arranged such that they substantially circumscribe a repeating
pattern of recessed areas 101 in the form of geometric shapes. The
geometric shapes may be contiguously arranged as depicted. The
geometric shapes may be diamonds or squares, as depicted (and
illustrated by dotted outlines 102a, 103a in FIG. 3A), or may have
other shapes, including but not limited to triangles, diamonds,
parallelograms, other polygons, circles, hearts, moons, etc. In
FIG. 3A, it can be seen also that the pattern of geometric shapes
repeats in the machine and cross directions at frequencies
determined by the dimensions of the shape circumscribed by outline
103a, where outline 103a is drawn through the centers of the
protrusion surfaces 100. It can be seen that the dimensions of the
shape circumscribed by outline 103a correspond with shape length
L.sub.S1 and shape width W.sub.S1 as shown in FIG. 3A. (Again,
length and width are designated with reference to the machine
direction MD.) Without intending to be bound by theory, within the
ranges of basis weights of spunbond nonwoven materials contemplated
herein, it is believed that the size of the repeating
geometrically-shaped recessed areas 101 may be impactful with
respect to optimizing both the apparent and actual desired visible
"pop" of the pattern.
[0109] It may be desired that the shapes circumscribed by the bond
impressions repeat at a frequency of from 99 to 149, or from 105 to
143, or even from 111 to 137 per meter, in either or both the
machine and cross directions, on the nonwoven web. Referring to
FIG. 3B, for example, this would means that length L.sub.s2 and/or
width W.sub.s2 may each be about 6.7 mm to 10.1 mm, or from 7.0 mm
to 9.5 mm, or even from 7.3 mm to 9 mm. Alternatively, it may be
desired that the repeating shapes defined by the bond impressions
(for example, as illustrated/suggested by the repeating square or
diamond shape defined by outline 103a, FIG. 3A), have areas from 52
mm.sup.2 to 78 mm.sup.2, or from 55 mm.sup.2 to 75 mm.sup.2, or
even from 58 mm.sup.2 to 72 mm.sup.2.
[0110] As noted, calender-bonding may be used to consolidate the
spunlaid fiber batt into a fabric-like nonwoven web and to impart
mechanical strength, e.g., tensile strength, to the web. Generally,
within the ranges contemplated herein, greater percentages of
protrusion surface area to total patterned roller surface area on a
roller formed with a given pattern impart greater tensile strength
to the web, than lesser percentages. However, this may come at the
cost of added stiffness in the web, which may negatively impact
tactile softness attributes. It is believed that a suitable balance
between imparting sufficient tensile strength for subsequent
processing and satisfactory structural strength in the finished
product, and preserving tactile softness attributes, may be struck
when the ratio of area of the protrusion surfaces (e.g., protrusion
surfaces 100, FIG. 3A) to the total patterned roller surface area
is from 16% to 35%, or from 17% to 30%, or even from 18% to
25%.
[0111] It will be noted in FIG. 3A that protrusion surfaces 100
appear to form interrupted paths, in the example depicted, along
directions indicated by arrows 104a, 104b. Without intending to be
bound by theory, it is believed that the interruptions provide at
least two beneficial effects. First, it is believed that the
resulting bond impressions in the web have the effect of simulating
the appearance of stitching, as in a quilt. Second, it is believed
that the interruptions in the bond paths provide a multitude of
natural hinge points at which the web may flex about the discrete
bonds, helping to preserve or enhance pliability in the web despite
the presence of the bonds. When a spunlaid batt is passed through a
nip formed by a calendering roller having the pattern depicted in
FIG. 3A, bonds among and between the fibers are formed beneath
protrusion surfaces 100. If these surfaces were continuous along
directions 104a, 104b instead of interrupted as shown, the
resulting bonds would also be substantially continuous along those
directions. This could cause the resulting nonwoven web to be more
stiff and less pliable, undesirably comprising its tactile softness
attributes.
[0112] It will also be noted in FIG. 3A that the directions 104a,
104b followed by the bonding pattern paths may be diagonal with
respect to the machine direction. The bond paths imposed on the
resulting web will be similarly diagonal with respect to the
machine direction. Without intending to be bound by theory, and
relative to the use of increased calender-bonding pressure and/or
roller temperature to form more fully developed bonds as described
herein, it is believed that these paths, when formed of more
fully-developed bonds, comprise diagonal paths or linear zones
along which the nonwoven web has relatively higher tensile strength
and resistance to elongation. It is believed that an interesting
effect may result. When these paths are diagonal relative the
machine direction and in a criss-crossing pattern as depicted, a
net-like structure may be present within the web. As a result,
drawing the nonwoven web under tension in the machine direction (as
it would be drawn in downstream manufacturing processes, e.g.,
laminating the nonwoven with a polymer film to form backsheet
material) may have the effect of causing the geometric shapes 101
to slightly protrude or "pop" in the z-direction out of the general
plane of the web material surface as it narrows in width
(exhibiting Poisson effect behavior), or "necks" slightly, as a
result of forces within the material under tension in the machine
direction, influenced by the net-like structure of diagonal paths
of higher tensile strength formed by the bonds.
[0113] It is believed that a pattern of diagonally-oriented bonding
paths, as suggested in FIGS. 3A and 3B, may be more effective for
producing the z-direction "pop" effect described above, than other
possible configurations. It is believed, further, that along such
diagonally-oriented bonding paths, a greater percentage of bonded
material along the paths will have a more dramatic impact than a
lesser percentage, because the bonding results in the
above-mentioned effect of forming a line along the nonwoven of
relatively greater tensile strength and resistance to elongation.
Thus, referring to FIG. 3B, it can be seen that a line 105 can be
traced a path of bond impressions 100a (line 105 is drawn through
the centers of bond impressions 100a, in the depicted example). In
order that path 105 exhibits sufficiently greater tensile strength
and resistance to elongation than neighboring/parallel lines or
paths in the material, it may be desirable that the Bond Length
Ratio of a segment along line 105 is between 35% and 99%. However,
as noted, it may be desirable not to impart too much stiffness to
the web (which compromises a tactile softness attribute). Thus, it
may be desirable that the Bond Length Ratio of a bond path be
between 35% and 80%, more preferably between 35% and 65%, and even
more preferably between 35% and 55%.
[0114] It has been learned that more fully-developed bonds and a
more highly-defined bond pattern may be more effectively achieved
when the protrusion surfaces 100 are polished such that they are
relatively smooth, rather than having a rougher, machined
surface.
[0115] In order to complement the z-direction "pop" effect, in
which the material forming unbonded areas 101a protrudes out of the
general plane approximated by the web surface, it may be desirable
that the pattern of bond impressions 100a (e.g., FIG. 3B) be
distinct to the naked eye. In order to achieve this, sufficient
force between the calendering rollers should be applied, in
combination with sufficient heating temperature. As a result, a
visibly distinct pattern of bonds may be achieved, and this pattern
will have measurable features. Depending upon bonding pressure and
temperature used, the shape and area of the protrusion surfaces 100
will be somewhat reflected in the shape and area of the bond
impressions in the nonwoven web. Generally it may be desired that
calender bonding pressure and/or roller temperature be adjusted so
as to cause the shape and area of protrusion surfaces 100 to be
substantially reflected in the shape and area of the bond
impressions.
[0116] It was previously believed that relatively lighter calender
bonding pressures and/or relatively cooler bond roller temperatures
were required for calender bonding, to avoid tightly binding down
fibers, such that they were no longer available to be fluffed by
downstream hydroengorging processes intended to enhance visual and
tactile softness attributes. Similarly, while creating more fully
developed bonds was thought to be required to improve tensile
strength properties, it was believed that creating more
fully-developed, rigid bonds through relatively greater calendering
pressures and/or roller temperatures would have the effect of
undesirably increasing stiffness of the nonwoven, unacceptably
compromising its tactile softness attributes. In short, it was
believed that to preserve or gain tactile and visual softness
signals, it was necessary to compromise tensile strength.
[0117] However, it has been discovered, surprisingly, that under
the circumstances and conditions described herein, negative effects
of greater bonding pressures and/or temperatures upon tactile
softness attributes may be insubstantial and/or may be overcome by
the positive effects upon visual softness attributes. More
particularly, it has been discovered that a more highly-defined
bond pattern and quilt "pop" may be enabled through use of
relatively increased calender bonding pressures and/or roller
temperatures, resulting in more fully-developed bonds, which
appears to be effective at creating a product that creates overall
visual impressions of softness that may overcome any negative
effects upon tactile softness signals resulting from increased
stiffness in the material.
[0118] Further, it has been discovered, surprisingly, that one
tactile softness signal, pliability (sometimes known as "drape"),
can be substantially maintained or only insubstantially affected
with the nonwoven materials under circumstances contemplated
herein, even where more fully developed bonds are created, using
bond patterns having features such as those described above.
Without intending to be bound by theory, it is believed that
interruptions in the bond paths, for example, such as those
described above (e.g., interruptions 106, FIG. 3B), may provide
natural hinge points at which the material may flex easily about
bonds, even in the presence of more fully developed bonds. Although
the phenomenon is not thoroughly understood, it is believed that
this hinge effect, combined with the multitude of relatively small
bond sites separated by unbonded areas such as described and
depicted herein (e.g., unbonded areas 101a, FIG. 3A), result in
effective substantial preservation of pliability or drape even when
the bond sites are more fully developed through relatively
increased calender bonding pressures and/or temperatures.
[0119] At the same time, creating more fully developed bond sites
may add tensile strength in the machine and/or cross directions.
Thus, counterintuitively, it has been discovered that tensile
strength can be substantially increased through creation of more
fully developed calender bonds, without a corresponding,
deleteriously substantial negative effect on a tactile softness
signal, pliability. This effect may be achievable using features of
roller patterns as described herein, with suitably adjusted
calender force/pressure and roller temperature, to impress a Bond
Area Percentage in the nonwoven web of at least 10%, preferably not
more than 20%, more preferably 10% to 17%, and even more preferably
10% to 15%.
[0120] Referring to FIGS. 3A and 3B by way of example, it is
believed that the size, shape and area of bond impressions 100a in
the nonwoven web product will somewhat, but not identically,
reflect the size, shape and area of calender roller protrusion
surfaces 100. It is believed that the extent to which the area(s)
of bond impressions 100a reflect the area(s) of roller protrusion
surfaces 100 may be affected by the bonding force/pressure between
the calender rollers at the nip, and/or the roller temperature, and
generally, that increasing bonding force/pressure and/or roller
temperature will increase the area of bond impressions 100a
relative the area of protrusion surfaces 100. Thus, if the area of
a protrusion surface 100 is from 0.74 mm.sup.2 to 1.12 mm.sup.2, or
from 0.84 mm.sup.2 to 1.02 mm.sup.2, or even from 0.88 mm.sup.2 to
0.098 mm.sup.2 as set forth above, it is believed that generally
the area of a corresponding bond impression will be somewhat less.
In order to achieve the visibly improved results realized in
Example 2 herein, bond impressions 100a were created having an
average surface area of 0.57.+-.0.06 mm.sup.2, resulting from
protrusion surfaces 100 having an average surface area of
approximately 0.93 mm.sup.2. In a prior version, using the same
basis weight spunbond batt and the same rollers, the resulting
average bond impression surface area was measured as 0.27.+-.0.02
mm.sup.2, resulting from a relatively lighter calender pressure
and/or roller temperature. It is believed that an increase in
calender pressure and/or roller temperature is at least partially
the cause for the difference.
[0121] Following calender bonding, the web may be subjected to a
hydroengorgement process such as described in U.S. Pat. App. Pub.
No. 2006/0057921. A distinguishing feature of hydroengorgement, as
compared with traditional hydroentanglement, is the use of
hydraulic jets to enhance the loft and softness attributes of a
nonwoven. However, prior use of hydroengorgement has not been fully
satisfactory for providing a nonwoven having both improved softness
and a bond pattern with a visually distinct appearance. The '921
application describes a hydroengorgement process involving
particular ranges of pressure, e.g., 180-240 bar (2,610-3,480
p.s.i.) applied to the water jet orifices, which was believed
required to obtain a desired amount of fluffing of the nonwoven
fibers, adding apparent and actual loft or caliper. However, it has
been discovered that substantially reducing the hydroengorgement
pressure from these magnitudes may still provide desired fluffing
without deleterious effects. It is believed that hydroengorgement
pressures of the magnitude specified in the '921 application may
result in a loss of distinctiveness and/or obscuring of the pattern
of bond impressions. Substantially reducing hydroengorgement
pressure and energy, and directing hydroengorgement jets at only
the inner-facing surface of the nonwoven (thus urging
fibers/portions thereof impinged by water jets toward the
outer-facing surface) appears to have had a contribution to
improving the definition and visual "pop" of the quilt appearance
on the outer-facing surface imparted by the roller pattern. A
reduced pressure of about 25-100 bars (360-1,450 p.s.i.) may be
employed for hydraulic treatment. More preferably, two injectors,
each at about 50 bars (725 p.s.i.) of pressure are used, providing
an energy transmission of about 0.02 kwhr/kg. It is believed that
the use of a one-sided hydroengorgement significantly improves the
softness attributes of the nonwoven while pushing fibers in between
bond areas to create a more pronounced appearance. Further, the
hydroengorgement may enhance the resilience of the pattern such
that it can maintain a pronounced appearance after being processed
into an article and packaged.
[0122] In addition to the features, methods and materials described
above, it is believed that the manner in which the nonwoven web is
adhered to the polymeric film, to form a backsheet laminate, may
have an impact on the quilted appearance of the backsheet. In
particular, use of a thermoplastic polymeric hot melt adhesive to
adhere the nonwoven web to a thin polymeric film to form a
backsheet laminate may enhance the quilted appearance. Without
intending to be bound by theory, it is believed that, following
lamination, the adhesive contracts slightly as it cools, causing
the film, and correspondingly, the laminate, to pucker slightly.
This may contribute to causing the unbonded areas of the nonwoven
(e.g., unbonded areas 101a, FIG. 3b), to protrude or pop slightly
in the z-direction.
[0123] If this theory is correct, it may also be desired to apply
the hot melt adhesive in a pattern such that adjacent areas and
patterns of the nonwoven and polymer film are adhered and not
adhered. This allows unadhered areas of the nonwoven to pop in the
z-direction away from the film when the laminate is shifted about,
such as during handling or wear, contributing to the quilted
appearance. Accordingly, in one example, adhesive may be applied in
1 mm wide strips extending along the machine direction, at 3 to 4
strips per centimeter along the cross direction. In another
example, adhesive may be applied in a spiral pattern, or series of
spiral patterns, leaving unadhered areas surrounded and
interspersed with adhered areas.
[0124] Further, the polymer film may be stretched slightly in the
machine direction prior to, and maintained in the stretched
condition during, lamination to the nonwoven web. In this event,
subsequent relaxation and elastic contraction of the film following
lamination may cause slight machine direction compression of the
nonwoven web and thereby promote z-direction protrusion of unbonded
areas thereof, potentially enhancing visual "pop" by yet another
mechanism. A polymer film may be stretched from 1% to 5% in
machine-direction length prior to lamination, or more preferably,
from 2% to 4%.
Example 1
[0125] An exemplary embodiment of the present invention, Sample A,
was a spunbond nonwoven made in a four beam process, laying down
four layers (layers A, B, C, D) of fibers, two layers formed of
ExxonMobil 3155 polypropylene and two layers formed of ExxonMobil
SFT315 polypropylene blend with the bottom layers of the nonwoven
being made from ExxonMobil 3155. Each layer contained 2.5% by
weight of a master batch containing about 30% by weight
polypropylene and 70% TiO.sub.2 (a whitener), corresponding to
about 1.75% by weight TiO.sub.2 for the layer. The spunbond
nonwoven was bonded using the bond pattern described for Example 2
below. The bottom side of the nonwoven was hydraulically treated
using two rows of jets, each at 50 bars (725 p.s.i.) pressure, for
a total energy transmission of 0.02 kwhr/kg.
[0126] By comparison, Control A was made from the same nonwoven
substrate and bond pattern with only about 0.3% of whitener in each
layer. Further, Control A was hydroengorged using a hydraulic
treatment on both sides of the nonwoven each side being subjected
to a row of jets at a pressure of 240 bars (3,480 p.s.i.).
[0127] An additional sample, Control B was made from the same
nonwoven with the same processing conditions as Sample A but
without any hydraulic treatments.
[0128] A third sample, Control C was made with the same nonwoven as
Sample A however the whitener distribution was limited to 1.6% on
the top layers with no whitener on the bottom layers. The nonwoven
was hydroengorged using 2 injectors at 100 bars (1,450 p.s.i.)
pressure on the top side, followed by 2 injectors at 250 bars
(3,626 p.s.i.) pressure on the bottom side.
[0129] In a comparison, Sample A had a significantly improved
appearance over Control A, both in raw nonwoven form and when
incorporated into an article. Sample A also had an improved
appearance over Control B and a significantly improved softness as
measured by a panel of testers. In comparison to Sample A, Control
C had an inferior visual appearance after manufacture and showed
significant deterioration in appearance after being incorporated
into an article and packaged. Table 1 sets forth properties of
Control A, Control B, Control C and Sample A.
TABLE-US-00001 TABLE 1 Description Control A Control B Control C
Sample A Process Conditions Whitener Distribution 0.3 .times. 4 2.5
.times. 4 1.6, 1.6, 2.5 .times. 4 (layers A-D), weight % 0, 0
Spinbelt speed, meters/m 420 440 420 440 HE Injector Pressures, 1
.times. 240, 2 .times. 0, 2 .times. 100, 2 .times. 0, C1, C2, bar 1
.times. 240 2 .times. 0 2 .times. 250 2 .times. 50 HE Energy,
kwhr/kg 0.20 0.00 0.26 0.02 Physical Properties Basis Weight, gsm
26.1 24.7 24.9 24.1 MD Tensile Strength, 795 918 673 938 gf/cm MD
Elongation, % 39.5 55.7 36.9 43.1 CD Tensile Strength, 489 449 347
489 N/cm CD Elongation, % 58.6 63.0 59.3 65.7 MD:CD 1.62 2.05 1.95
1.92 Air Perm, m.sup.3/m.sup.2/min 170 163 192 171 Caliper, mm --
0.275 0.271 0.296 Opacity, % 33.2 47.8 33.6 45.7 Hand Panel Survey
Not 0 Not 10 Tested Tested Quilt Definition of Poor Very Good
Excellent Nonwoven Good Quilt Definition after Poor Fair Excellent
Packaging
Example 2
[0130] An improved backsheet laminate including an improved
spunbond nonwoven web laminated/adhered to a polymeric film was
manufactured. The nonwoven web was calender-bonded in a pattern,
between the nip between a pattern calender roller and a smooth
calender roller as described herein, to impart a pattern of bond
impressions as schematically suggested in FIG. 3B. The improved web
had a basis weight of about 25 gsm and comprised PP.
[0131] The web was manufactured by First Quality Nonwovens, Inc.,
Great Neck, N.Y., using a calender roller bearing a repeating "P11"
pattern as schematically depicted in FIG. 3A, as provided by The
Procter & Gamble Company, Cincinnati, Ohio, and manufactured by
Ungricht Roller & Engraving Technology (A.+E. Ungricht GmbH+Co
KG), Monchengladbach, Germany. Referring to FIG. 3A, the
engraving/machining specifications for the roller pattern were such
that W.sub.S1 and L.sub.S1 were each 8.077 mm; W.sub.P1 was 1.69
mm; and L.sub.p1 was 1.1 mm, such that the protrusion surface 100
areas were each 0.93 mm.sup.2.
[0132] The improved laminate had a dramatically improved, visually
distinct quilted appearance and exhibited a dramatically improved
visible pattern of light and shadow under varying lighting
conditions, as compared with prior versions. The bond impressions
were more visible to the naked eye, and more clearly defined. The
Total Bond Area was estimated from the measured Average Individual
Bond Area and the roller pattern repeat dimensions (8.077 mm each
way) as approximately 12% to 13%.
[0133] Various features of the resulting improved nonwoven web and
laminate were measured and compared with those of prior versions of
nonwoven webs and laminates formed therewith, and having similar
calender bonding patterns. It is believed the improved quilted
appearance resulted from a combination of one or more of increased
Opacity, increased Average Measured Height, increased Average
Individual Bond Area and/or other features. As can be seen in Table
2, the improved nonwoven web also had improved tensile strength in
both machine and cross directions over the prior versions, except
for machine direction tensile strength compared with prior version
C; but version C had approximately 52% greater basis weight.
TABLE-US-00002 TABLE 2 Nonwoven Web Nonwoven Web Nonwoven Nonwoven
Aver- Average Basis Weight MD Tensile CD Tensile Opacity of Total
age Measured Individual (gsm)/ Strength Strength Opacity of
Nonwoven Stiffness Height Bond Area Sample construction (gf/cm)
(gf/cm) Laminate Web (g/f) (.mu.m) (mm.sup.2) Improved ~25/spunlaid
970 441 76 52 8.7 318 0.57 Prior ~25/spunlaid 679 298 72 34 7.4 170
0.27 Version A Prior ~25/spunlaid 822 266 68 32 6.6 274 0.27
Version B bicomponent fiber Prior ~38/carded 1,051 181 70 39 13.9
354 0.54 Version C
In-Bag Compression Measurement Test
I. Determine Free Stack Height
[0134] Equipment [0135] Universal Diaper Packaging Tester (UDPT),
including a vertical sliding plate for adding weights. It is
counter-balanced by a suspended weight to assure that no downward
force is added from the vertical sliding plate assembly to the
diaper package at all times. The UDPT is available from Matsushita
Industry Co. LTD, 7-21-101, Midorigaoka-cho, Ashiya-city, Hyogo
JAPAN. Zip code: 659-0014. For further details concerning this
Tester, see U.S. Pat. App. Pub. No. 2008/0312624. [0136] A 850 g
(.+-.5 g) weight. [0137] Stopwatch with an accuracy to 1
second.
[0138] Test Procedure
[0139] A) Apparatus Calibration [0140] Pull down the vertical
sliding plate until its bottom touches the tester base plate.
[0141] Set the digital meter located at the side of the vertical
sliding scale to zero mark. [0142] Raise the vertical sliding plate
away from the tester base plate.
[0143] B) Definitions [0144] Before-bagger free height refers to
the free height data measured on 10 pads of fresh diapers. [0145]
Fresh Diapers--10 diapers that have never been compressed (stack
should be removed (where safely possible) immediately after exit
from stacker, before any compression has occurred. If this is not
possible, they should be removed from the fingers of a safely
stopped stacker chain). [0146] Out-bag free height designates the
free height data measured on 10 pads of aged diapers. [0147] Aged
Diapers--10 diapers that have been held under compression for
approximately 1 minute and/or longer (i.e. 10 diapers come from a
freshly opened diaper package).
[0148] C) Free Height Measurement [0149] Select 10 adjacent pads of
diapers out of the middle from an appropriate source; Fresh diapers
for before-bagger free height; Aged diapers for out-of-bag free
height. [0150] Neatly stack these 10 pads of diapers underneath the
vertical sliding plate. (Align the center of the top pad directly
below the central counter sunk hole of the vertical sliding plate.)
[0151] Place the 850 g weight onto the vertical sliding plate.
[0152] Allow the vertical sliding plate to slide down until its
bottom lightly touches desired highest point of the stack. [0153]
Measure the stack dimensions in mm by reading the value that
appears on the digital meter. [0154] Remove the weight. [0155]
Raise the vertical sliding plate away from the stack and remove the
stack. [0156] Record the stack height reading to the nearest 1 mm
shown on the digital meter.
[0157] Procedure--Aging Profile [0158] A) Collect a minimum of
three data points from different sample sets e.g., Measure first
point from fresh diapers, e.g., measure second point from diapers
being aged in bag for 30 mm/1 hr/6 hr/12 hr/24 hr, e.g., measure
third point from diapers being aged in bag for 5 days or longer.
[0159] B) Repeat the three steps as described in "Test Procedure"
steps A), C), and D).
[0160] Procedure--Out-of-Bag Free Height Recovery [0161] A) Collect
10 pads of fresh/aged diapers. [0162] B) Repeat the first two steps
as described in "Test Procedure" steps A) and C). [0163] C) Repeat
the steps above for general free height measurement except changing
the waiting time (i.e., measure first point at 1 min and remaining
points at 30 mm/1 hr/6 hr/12 hr/1 day/3 days/5 days, or
longer).
[0164] Calculation/Reporting [0165] Report Sample Identification,
i.e. complete description of product being tested (product brand
name/size). [0166] Report the determined value for all measurement
to the nearest 1 mm. [0167] NOTE: In case of a series of
measurements report the number of tested samples, and
calculate/report the Average, Standard deviation, Minimum and
Maximum of the values. [0168] Report the Production Date of the
measured package (taken from package coding). [0169] Report the
Testing Date and Analytical Method used (GCAS). II. Determine
in-Bag Stack
[0170] Equipment [0171] Universal Diaper Packaging Tester (UDPT),
including a vertical sliding plate for adding weights. It is
counter-balanced by a suspended weight to assure that no downward
force is added from the vertical sliding plate assembly to the
diaper package at all times. The UDPT is available from Matsushita
Industry Co. LTD, 7-21-101, Midorigaoka-cho, Ashiya-city, Hyogo
JAPAN. Zip code: 659-0014. [0172] A 850 g (.+-.5 g) weight.
[0173] Definitions [0174] "Package Width" is defined as the maximum
distance between the two highest bulging points along the same
compression stack axis of a diaper package. [0175] In-Bag Stack
Height=(Package Width I Pad Count Per Stack).times.10 pads of
diapers.
[0176] Apparatus Calibration [0177] Pull down the vertical sliding
plate until its bottom touches the tester base plate. [0178] Set
the digital meter located at the side of the vertical sliding scale
to zero mark. [0179] Raise the vertical sliding plate away from the
tester base plate.
[0180] Test Procedure [0181] Put one of the side panel of the
diaper package along its width standing at the center of the tester
base plate. Make sure the horizontal sliding plate is pulled to the
right so it does not touch the package being tested. [0182] Add the
850 g weight onto the vertical sliding plate. [0183] Allow the
vertical sliding plate to slide down until its bottom lightly
touches desired highest point of the package. [0184] Measure the
package width in mm (distance from the top of the base plate to the
top of the diaper package). Record the reading that appears on the
digital meter. [0185] Remove the 850 g weight. [0186] Raise the
vertical sliding plate away from the diaper package. [0187] Remove
the diaper package.
[0188] Calculation/Reporting [0189] Calculate and report the
"In-Bag Stack Height"=(Package Width I Pad Count Per
Stack).times.10. [0190] Report Sample Identification, i.e. complete
description of product being tested (product brand name/size).
[0191] Report the determined value for each measurement
(Length/Width/Front-to-Back) to the nearest 1 mm. [0192] NOTE: In
case of a series of measurements report the number of tested
samples, and calculate/report the Average, Standard deviation,
Minimum and Maximum of the values. [0193] Report the Production
Date of the measured package (taken from package coding). [0194]
Report the Testing Date and Analytical Method used (GCAS).
III. Calculate %
[0194] [0195] Calculate %: 1-(In-Bag Stack Height)/(Free Stack
Height)=%
Opacity Measurement Method
[0196] The opacity of a material is the degree to which light is
blocked by that material. A higher opacity value indicates a higher
degree of light block by the material. Opacity may be measured
using a 0.degree. illumination/45.degree. detection,
circumferential optical geometry, spectrophotometer with a computer
interface such as the HunterLab LabScan XE running Universal
Software (available from Hunter Associates Laboratory Inc., Reston,
Va.). Instrument calibration and measurements are made using the
standard white and black calibration plates provided by the vendor.
All testing is performed in a room maintained at about
23.+-.2.degree. C. and about 50.+-.2% relative humidity.
[0197] Configure the spectrophotometer for the XYZ color scale, D65
illuminant, 10.degree. standard observer, with UV filter set to
nominal. Standardize the instrument according to the manufacturer's
procedures using the 1.20 inch port size and 1.00 inch area view.
After calibration, set the software to the Y opacity procedure.
[0198] To obtain the specimen, lay the sample flat on a bench, body
facing surface downward, and measure the total longitudinal length
of the article. Note a site 33% of the total length from the front
waist of the article along the longitudinal axis and a second site,
33% of the total length from the back waist of the article.
Carefully remove the backsheet laminate, consisting of both the
film and nonwoven web, from the garment-facing side of the article.
A cryogenic spray, such as Cyto-Freeze (obtained from Control
Company, Houston, Tex.), may be used to separate the backsheet
laminate from the article. Cut a piece 50.8 mm by 50.8 mm centered
at each site identified above. Precondition samples at about
23.degree. C..+-.2 C..degree. and about 50%.+-.2% relative humidity
for 2 hours prior to testing.
[0199] Place the specimen over the measurement port. The specimen
should completely cover the port with the surface corresponding to
the garment-facing surface of the article directed toward the port.
Cover the specimen with the white standard plate. Take a reading,
then remove the white tile and replace it with black standard tile
without moving the specimen. Obtain a second reading, and calculate
the opacity as follows:
Opacity=Y value.sub.(black backing)/Y value.sub.(white
backing).times.100
[0200] A total of five identical articles are analyzed and their
opacity results recorded. Calculate and report the average opacity
and standard deviation for the 10 backsheet laminate measurements
to the nearest 0.01%.
[0201] Using the same specimens as above, remove the nonwoven web
from the film layer for anlysis. The cryogenic spray can once again
be employed. Precondition samples at about 23.degree. C..+-.2
C..degree. and about 50%.+-.2% relative humidity for 2 hours prior
to testing. In like fashion, analyze the nonwoven web layer
following the above procedure. Calculate and report the average
opacity and standard deviation for the 10 nonwoven web measurements
to the nearest 0.01%.
Average Measured Height Method
[0202] Average Measured Height is measured using a GFM Primos
Optical Profiler instrument commercially available from
GFMesstechnik GmbH, Teltow/Berlin, Germany. The GFM Primos Optical
Profiler instrument includes a compact optical measuring sensor
based on digital micro-mirror projection, consisting of the
following main components: a) DMD projector with 1024.times.768
direct digital controlled micro-mirrors; b) CCD camera with high
resolution (1300.times.1000 pixels); c) projection optics adapted
to a measuring area of at least 27.times.22 mm; d) recording optics
adapted to a measuring area of at least 27.times.22 mm; e) a table
tripod based on a small hard stone plate; f) a cold light source
(an appropriate unit is the KL 1500 LCD, Schott North America,
Inc., Southbridge, Mass.); g) a measuring, control, and evaluation
computer running ODSCAD 4.14-1.8 software; and h) calibration
plates for lateral (x-y) and vertical (z) calibration available
from the vendor.
[0203] The GFM Primos Optical Profiler system measures the surface
height of a sample using the digital micro-mirror pattern fringe
projection technique. The result of the analysis is a map of
surface height (z axis) versus displacement in the x-y plane. The
system has a field of view of 27.times.22 mm with a resolution of
21 microns. The height resolution should be set to between 0.10 and
1.00 micron. The height range is 64,000 times the resolution. All
testing is performed in a conditioned room maintained at about
23.+-.2.degree. C. and about 50.+-.2% relative humidity.
[0204] To obtain the specimen, lay the sample flat on a bench, body
facing surface downward, and measure the total longitudinal length
of the article. Note a site 33% of the total length from the front
waist of the article along the longitudinal axis and a second site,
33% of the total length from the back waist of the article.
Carefully remove the nonwoven outer cover from the garment-facing
side of the article. A cryogenic spray, such as Cyto-Freeze
(obtained from Control Company, Houston, Tex.), may be used to
separate the nonwoven from the underlying film layer. Cut a piece
40 mm by 40 mm centered at each site identified above. Precondition
samples at about 23.degree. C..+-.2 C..degree. and about 50%.+-.2%
relative humidity for 2 hours prior to testing.
[0205] Turn on the cold light source. Select settings on the cold
light source to give a reading of 3000K on the display (typically 4
and E). Open the ODSCAD 4.14-1.8 Software and select "Start
Measurement" and then "Live Pic". Calibrate the instrument
according to manufacturer's specifications using the calibration
plates for lateral (x-y) and vertical (z) available from the
vendor.
[0206] Place the 40 mm by 40 mm specimen of nonwoven outer cover,
clothing surface upward, under the projection head and on top of a
neutral gray surface (WhiBal White Balance Reference, PictureFlow
LLC, Melbourne, Fla.). Ensure that the sample is lying flat,
without being stretched. This may be accomplished by taping the
perimeter of the sample to the surface or placing it under a
weighted frame with an inside dimension of 30 mm.times.30 mm.
[0207] Using the "Pattern" command, project the focusing pattern on
the surface of the specimen. Position the projection head to be
normal to the sample surface. Align the projected cross hair with
the cross hair displayed in the software. Focus the image using the
projector head height adjustment knob. Adjust image brightness
according to the instrument manufacturer's instruction by setting
the "Projection" value to 10, and then changing the aperture on the
lens through the hole in the side of the projector head. Optimum
illumination is achieved when the lighting display indicator in the
software changes from red to green. Due to variations in instrument
configurations, different brightness parameters may be available.
Always follow the instrument manufacturer's recommended procedures
for proper illumination optimization.
[0208] Select the Technical Surface/Standard measurement type.
Operating parameters are as follows: Utilization of fast picture
recording with a 3 frame delay. A two level Phasecode, with the
first level being defined as an 8 pixel strip width with a picture
count number of 24, and the second level being defined as a 32
pixel strip width with a picture count number of 6. A full Graycode
starting with pixel 1 and ending with pixel 1024. A Prefiltering
routine including the removal of invalid pixels, a 5 by 5 median
filter, and a 3 by 3 average filter.
[0209] Select "Measure" to capture and digitalize the image. The
specimen must remain still during this procedure to avoid blurring
of the captured image. The image will be captured in approximately
20 seconds. Save the height image and camera image files.
[0210] Load the height image into the analysis portion of the
software via the clipboard. Zoom in on a region of interest (ROI)
encompassing a single repeating pattern of bond impressions and
unbonded area. Using the polygon drawing tool manually outline four
individual bond impressions around the perimeter of the unbonded
area (see example in FIG. 4B). From "View" select "Histogram of
height picture". Select the number of classes as 200 and calculate
the frequency histogram. Save the bond impression height file.
Returning to the height image, cancel the polygon markings drawn on
the bond impressions. Next, using the polygon drawing tool,
manually outline the unbonded area surrounded by the bond
impressions (see example in FIG. 4A). Once again, from "View"
select "Histogram of height picture". Select the number of classes
as 200 and calculate the frequency histogram. Save the unbonded
area histogram file.
[0211] Open the histogram file of the bond impressions, determine
the height range value at, or nearest to 50%. Record bond
impression height to the nearest 1 micrometer. Open the histogram
file of the unbonded area, determine the height range value at, or
nearest to 90%. Record the unbonded area height to the nearest 1
micrometer. Measured Height is calculated as follows:
Measured Height=unbonded area height-bond impression height
[0212] Measured Height is measured at two separate ROI's for each
of the specimens (i.e., from front of article and back of article)
to give four measures per test article. A total of three test
articles are analyzed in like fashion. Calculate the Average and
standard deviation for all twelve measured Measured Heights and
report to the nearest 1 micrometer.
Tensile Strength Measurement Method
[0213] Tensile Strength is measured on a constant rate of extension
tensile tester with computer interface (a suitable instrument is
the MTS Alliance using Testworks 4.0 Software, as available from
MTS Systems Corp., Eden Prairie, Minn.) using a load cell for which
the forces measured are within 10% to 90% of the limit of the cell.
Both the movable (upper) and stationary (lower) pneumatic jaws are
fitted with rubber faced grips, wider than the width of the test
specimen. All testing is performed in a conditioned room maintained
at about 23.degree. C..+-.2 C and about 50%.+-.2% relative
humidity.
[0214] To obtain the specimen for CD tensile, lay the sample flat
on a bench, body facing surface downward, and measure the total
longitudinal length of the article. Note a site 25% of the total
length from the front waist of the article along the longitudinal
axis and a second site, 25% of the total length from the back waist
of the article. Carefully remove the nonwoven outer cover from the
garment-facing side of the article. A cryogenic spray, such as
Cyto-Freeze (obtained from Control Company, Houston, Tex.), may be
used to separate the nonwoven outer cover from the underlying film
layer. Cut a specimen, with a die or razor knife, which is 50.8 mm
wide along the longitudinal axis of the sheet and least 101.6 mm
long along the lateral axis of the sheet, centered at each of the
sites identified above.
[0215] In like fashion prepare MD tensile specimens from a second
set of identical samples. Here, after removing the nonwoven outer
cover, cut a specimen, with a die or razor knife, which is at least
101.6 mm wide along the longitudinal axis of the sheet and 50.8 mm
long along the lateral axis of the sheet, centered at each of the
sites identified above. Precondition both CD and MD specimens at
about 23.degree. C..+-.2 C..degree. and about 50%.+-.2% relative
humidity for 2 hours prior to testing.
[0216] For analyses, set the gage length to 50.8 mm. Zero the
crosshead and load cell. Insert the specimen into the upper grips,
aligning it vertically within the upper and lower jaws and close
the upper grips. Insert the specimen into the lower grips and
close. The specimen should be under enough tension to eliminate any
slack, but less than 0.05 N of force on the load cell.
[0217] Program the tensile tester to perform an extension test,
collecting force and extension data at an acquisition rate of 50 Hz
as the crosshead raises at a rate of 100 mm/min until the specimen
breaks. Start the tensile tester and data collection. Program the
software to record Peak Force (gf) from the constructed force (gf)
verses extension (mm) curve. Calculate tensile strength as:
Tensile Strength=Peak Force (gf)/width of specimen (cm)
[0218] Analyze all CD tensile specimens. Record Tensile Strength to
the nearest 1 gf/cm. Analyses are performed on specimens from the
two sites on the article. A total of five test articles are
analyzed in like fashion. Calculate and report the average and
standard deviation of Tensile Strength to the nearest 1 gf/cm for
all ten measured CD specimens.
[0219] Next run all MD tensile Specimens. Record Tensile Strength
to the nearest 1 gf/cm. Analyses are performed on specimens from
the two sites on the article. A total of five test articles are
analyzed in like fashion. Calculate and report the average and
standard deviation of Tensile Strength to the nearest 1 gf/cm for
all ten measured MD specimens.
Image Analysis of Bond Impressions
[0220] Area and distance measurements are performed on images
generated using a flat bed scanner capable of scanning at a
resolution of at least 4800 dpi in reflectance mode (a suitable
scanner is the Epson Perfection V750 Pro, Epson, USA). Analyses are
performed using ImageJ software (Vs. 1.43u, National Institutes of
Health, USA) and calibrated against a ruler certified by NIST.
[0221] To obtain the specimen, lay the sample flat on a bench, body
facing surface downward, and measure the total longitudinal length
of the article. Note a site 33% of the total length from the front
waist of the article along the longitudinal axis and a second site,
33% of the total length from the back waist of the article.
Carefully remove the nonwoven outer cover from the garment-facing
side of the article. A cryogenic spray, such as Cyto-Freeze
(obtained from Control Company, Houston, Tex.), may be used to
separate the nonwoven from the underlying film layer. Cut a piece
80 mm by 80 mm centered at each site identified above. Precondition
samples at about 23.degree. C..+-.2 C..degree. and about 50%.+-.2%
relative humidity for 2 hours prior to testing.
[0222] Place the specimen on the flat bed scanner, body side
surface facing upward, with the ruler directly adjacent. Placement
is such that the dimension corresponding to the MD of the nonwoven
is parallel to the ruler. A black backing is placed over the
specimen and the lid to the scanner is closed. Acquire an image
composed of the nonwoven and ruler at 4800 dpi in reflectance mode
in 8 bit grayscale and save the file. Open the image file in ImageJ
and perform a linear calibration using the imaged ruler. Reference
will be made to FIG. 3B as an example of a repeating pattern of
bond impressions. These measures are equally applicable to other
bond shapes and repeating bond patterns.
[0223] Average Individual Bond Area
[0224] Enlarge a ROI such that edges of the bond impression can be
clearly determined. With the area tool, manually trace the
perimeter of a bond. Calculate and record the area to the nearest
0.001 mm.sup.2. Repeat for a total of ten non-adjacent bonds
randomly selected across the total specimen. Measurements are made
on both specimens from each article. A total of three identical
articles are measured for each sample set. Calculate the average
and standard deviation of all 60 bond area measurements and report
to the nearest 0.001 mm.sup.2.
[0225] Bond Path/Bond Length Ratio
[0226] Identify a single, complete repeating series of bond
impressions forming a path and enlarge the image such that the
repeating series fills the field of view. Draw a line along the
path that connects and extends through all bond impressions in the
series (e.g., FIG. 3B, line 105). Measure the dimensions along the
line that are included within the bond impressions (e.g. in FIG.
3B, D.sub.1, D.sub.2, D.sub.3). Next, measure the distance of the
line segment from the leading edge of the first bond impression in
the repeating series to leading edge of the first bond impression
in the next adjacent series along the line segment (e.g. in FIG.
3B, D.sub.o). Calculate the sum of the lengths of the bonds along
the line segment (e.g. D.sub.1+D.sub.2+D.sub.3), divided by the
length of the line segment, (e.g. D.sub.o), x100%. Record the Bond
Path/Bond Length Ratio to the nearest 0.001. Repeat for a total of
five non-adjacent ROI's randomly selected across the total
specimen. Measurements are made on both specimens from each
article. A total of three identical articles are measured for each
sample set. Calculate the average and standard deviation of all 60
bond Path/Length Ratio measurements and report to the nearest 0.001
units. Note for irregularly-shaped bond impressions forming a
repeating series, locate a line so as to find the maximum sum of
the lengths of the bond impressions measurable therealong.
[0227] Bond Area Percentage
[0228] Identify a single repeat pattern of bond impressions and
unbonded areas and enlarge the image such that the repeat pattern
fills the field of view. In ImageJ draw a box that encompasses the
repeat pattern. For the example shown in FIG. 3B, this would be a
box, W.sub.S2 wide and L.sub.S2 long. Note, in the example shown in
FIG. 3B, the shared bond impressions at the corners are divided in
half along the longitudinal or lateral direction as appropriate.
Calculate area of the box and record to the nearest 0.01 mm.sup.2.
Next, with the area tool, trace the individual bond impressions or
portions thereof entirely within the box and calculate the areas of
all bond impressions or portions thereof that are within the box.
Record to the nearest 0.01 mm.sup.2. Calculate as follows:
Percent Bond Area=(Sum of areas of bond impressions within
box)/(area of box).times.100%
Repeat for a total of five non-adjacent ROI's randomly selected
across the total specimen. Record as Percent Bond Area to the
nearest 0.01%. Measurements are made on both specimens from each
article. A total of three identical articles are measured for each
sample set. Calculate the average and standard deviation of all 30
of the percent bond area measurements and report to the nearest
0.001 units.
Stiffness
[0229] Stiffness of the nonwoven outer cover was measured in
accordance with ASTM D6828-02. For analysis a 76.2 mm by 76.2 mm
square specimen was used instead of the 100 mm by 100 mm specimen
recited in the standard.
[0230] To obtain the specimen, lay the sample flat on a bench, body
facing surface downward, and measure the total longitudinal length
of the article. Note a site 25% of the total length from the front
waist of the article along the longitudinal axis and a second site,
25% of the total length from the back waist of the article.
Carefully remove the nonwoven outer cover from the garment-facing
side of the article. A cryogenic spray, such as Cyto-Freeze
(obtained from Control Company, Houston, Tex.), may be used to
separate the nonwoven from the underlying film layer. Cut a piece
76.2 mm by 76.2 mm centered at each site identified above.
Precondition samples at about 23.degree. C..+-.2 C..degree. and
about 50%.+-.2% relative humidity for 2 hours prior to testing.
[0231] Stiffness measurements are made on both specimens from each
article. A total of three identical articles are measured for each
sample set. Calculate the average and standard deviation of the six
Total Stiffness results and report to 0.01 g.
[0232] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0233] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0234] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *